A recently developed metallurgical furnace intended for finishing a semi-finished steel melt, has a contour generally resembling a Bessemer convertor and, like that convertor, is made so that it can be tilted between the vertical and horizontal positions. However, it is intended for finishing operations requiring the addition of heat while the melt is being dephosphorized or the like, as contrasted to the Bessemer convertor's function of converting blast-furnace iron to steel.
For the addition of heat, the bottom of this furnace is provided with a channel-type electric inductor extending diagonally so that when the furnace is vertical, the inductor can add heat to the melt, and when the furnace is horizontal, the inductor channel can retain sump metal, the side of the furnace that is downward when the furnace is horizontal, having a tap hole that can be opened for tapping the melt after its finishing.
For the introduction of dephosphorizing agents, alloys, or whatever is required to finish the melt in the furnace, a blast nozzle extends through the bottom of the furnace and through which the finishing materials, in particulate form, are blasted into the melt, being carried by a pressurized gas, normally a gas that is inert relative to the melt.
In operation, this recently developed furnace is vertically positioned to receive the melt from the primary melter, which may be an electric arc furnace, for example. To prevent the melt from flowing backwardly through the nozzle, the latter is supplied with a blast of the inert gas, thus holding up the melt from entering the nozzle during the charging. During the finishing operation, the blast is supplied with the finishing or alloying materials and, when finished, the furnace is turned to its horizontal position for tapping, the blast nozzle being positioned so that at that time it is above the level of the melt, although for various reasons the nozzle may continue to be supplied with pressurized gas.
With the furnace in its vertical position and receiving the charge of molten metal, and during the finishing period, any failure of the blast, a possibility due to human error, broken blast connections, power failure, etc., leaves the melt free to run backwardly through the nozzle and escape from the furnace. Such a melt-escape presents a serious hazard to the furnace operating personnel, and, of course, to the equipment surrounding the furnace.
During the charging and refining phases, the nozzle is directly exposed to the thermal and erosive effects of the melt and, therefore, it is desirable that the nozzle be made so that it can be removed easily either for servicing or for replacement by a corresponding nozzle. The furnace vessel is, of course, made with a refractory lining surrounded by a metal shell, both having an opening for the nozzle, and the furnace lining should not be damaged during removal and replacement of the nozzle. The outer end of the nozzle can have a metal flange that is removably bolted or otherwise fastened to the metal shell.
Under the obviously severe operating conditions of the nozzle when in use, there is a risk that the nozzle might sinter to the furnace lining and thus become stuck together. It follows that removal and replacement of the nozzle presents a second problem in addition to the first problem of the possibility of a metal break-out.